Contact initiating apparatus for alarm purposes



O. l. ULLMAN July 16, 1957 CNTACT INITIATING APPARATUS FOR ALARMPURPOSES Filed Nov. 9. 1954 A United States Patent CONTACT INITIATINGAPPARATUS FOR ALARM PURPOSES Otto Ingemar Ullman, Storangen, SwedenApplication November 9, 1954, Serial No. 467,871

Claims. (Cl. 200-42) The present invention relates to alarm devices andmore particularly to devices for the automatic activation of alarms toprevent unauthorized access to confined spaces provided with accessmeans.

An object of the invention is to provide a reliable and improved contactinitiating apparatus for the automatic activation of alarms.

A further object of the invention is to provide an inexpensive contactinitiating apparatus which will automatically release an alarm ifdisabled.

Another object of the invention is to provide a contact initiatingapparatus which will :automatically release `an alarm if removed fromthe object to be protected or if subjected to raised temperatures.

The invention will be more fully explained hereinafter with reference toa preferred embodiment thereof as illustrated in the attached drawing.The sole figure in the drawing illustrates, in a perspective view, acontact initiating apparatus provided in accordance with the invention.

Referring to the drawing, a casing 1 of light metal is internallyfurnished with Ibracket-lik-e members 2 located in a vertical row ateach side of the casing. Detach- `ably inserted to rest on saidbracket-like members are two lshelves 3 and 4 of insulating materialsuch as, for example, hard rubber. The shelf 3 is provided in the centerthereof with a partition 5. VOn each side of said partition, the shelf 3is provided with three contact pins or points `6, upon which steel balls7 freely rest. Furthermore a bimetallic spring 8 is fixed intermediateits ends to said partition.

The inner end of -a two-wire lead 21 connected to an alarm apparatus,such as a bell or the like (not shown), is clamped to the shelf 4 bymeans of a clamp 9 and said lead is brought out of the apparatus throughan aperture in the bottom of the casing 1. One of the wires of said lead21 is by means of a wire 14 connected to one of the contact pins 6 onthe right side of the partition 5, which pin 6 in turn by means of alead 10 is connected to one of the contact pins 6 on the left side ofsaid partition. The second wire of said lead 21 is connected via a lead13 to a suitable resistance 11, which in turn is connected by means ofIa lead 12 to the second contact pin 6 on the left `side of thepartition 5, which latter pin by means of a lead 23 is connected to thesecond pin 6 on the right side of the partition.

As will be evident from the drawing the casing 1 in front -of the ballsand electric connections is closed by means of a sheet or plate 1S ofinsulating material. Close to said plate 15 is inserted a magnet 16having a groove 24 for receiving a brass bar 17 which is fixed to thecasing at each end by means of a screw 18 and 19 respectively. Placedclose to said brass lbar 17 is a further insulating plate 20. Thus thelower part of the casing 1 is substantially closed whereas the upperdome-like portion of `said casing is open for being placed over ahandle, keyway, or latch 22 of the door of a safe or like.

icc

The alarm initiating apparatus according to the invention operates asfollows. When a safe or the like `is to be protected againstilligitimate access, the casing 1 is placed with the upper domed portioncovering the handle, keyway, or latch thereof. In this position themagnet 16 -adheres to the metal of the safe thus providing aself-supporting attachment of the entire apparatus to said safe. Anelectric circuit is assumed to be closed through said apparatus by wayof the lead 21. In an attempt at removing or displacing said casing inrelation to said safe, the balls will be lsubjected to :a shaking actionso that the circuit will be alternately yopened and closed giving riseto an alarm signal.

:More particularly, the balls 7 constitute switches between theterminals 6. When the balls 7 are at rest, `the terminals 6 areelectrically connected, and this electrical connection is interruptedonly by such motion of the balls 7 as will cause them to lose mechanicalcontact with the terminals 6.

One physical principle which is utilized to make the balls 7 effectivein an alarm system is the phenomenon which occurs when a magneticcircuit is opened. The magnet 16 has a `C-shaped cross-section whichforms a closed magnetic path with the metallic object upon which themagnet rests. Most of the iiux is contained within the closed path.

When the device and, therefore, the magnet 16 is removed from themetallic wall, the magnetic path is broken and the iiux lines iindsubstantially equal perme- ,ance in the all of the space surrounding themagnet and, therefore, encounter the balls 7 which as free bodies in amagnetic field are moved. This motion causes the terminals -6 to bedisconnected despite the smoothness with which the device is removedfrom the safe.

In an attempt to short-circuit or by-pass the apparatus byshort-circuiting the lline 21 at any point, the resistance in thecircuit or `circuits would be changed and therewith the Voltage. Thischange of the voltage would bring about a signal. The only possible Wayof preventing such a signal would be to interpose a resistance (of the`same value as resistor 11) in the -short-circuiting circuit. This wouldbe extremely ditlicult to a person not familiar with intern-a1construction of the devi-ce and must be carried out with extraordinarycare.

It is further not possible by means of welding to by-pass the contactapparatus of the invention due to the provision of the bimetallic spring8 which will react to an increase in temperature (due to heating in thevicinity of apparatus) by displacing the contact balls out of theirpositions upon the contact points so as to give rise to a signal. Itwould be substantially impossible to insulate the contact apparatusthermally such that the bimetallic spring would be prevented fromoperating. The spring, further, has another function which is to make itimpose sible, by welding or otherwise,`to force through the casing ofthe contact apparatus and to lock the contact members or eifectshort-circuiting between the same and the earlier mentioned resistances.Finally, it also renders impossible attempts to deprive the magnet 16 ofits magnetism by heating.

The contact apparatus provided by the invention offers an effectiveprotection against burglary and thus protects articles of considerablevalue. Furthermore, it is readily standardized. Finally, it does notrequire any expensive mountings and may be attached to any object wherea magnetizable element is available.

Having now particularly described and ascertained the nature of my saidinvention and which manner the same is to be performed, I declare, thatwhat I claim is:

1. In a signal initiating switch apparatus for preventing illegitimateaccess to the operating means for the latch mechanism of safes andsimilar depository compartments or rooms having a magnetic covering atleast around said operating means, a magnet adapted to adhere to saidmagnetic covering as linked by magnetic ux to support the entire switchapparatus on said covering; anball switch mechanism located in thevicinity of said yniagnetand comprising a magnetic ball, metalliccontact points in an electric switch circuitof which said ball isamember-,said

ball freely resting on said Contact points, a casing enclos ing saidmagnet and said ball switch in an inaccessible manner when in mountedposition and cup-*formed member integral with said casing to receivesaid operating means for the latch mechanism of the safe with the magnetadhering to said covering. a I l 2. A signalinitiating switchapparatiisfas claimed in claim 1, comprising a bimetal spring;positiohed'adjacent the ball and adapted to move 'said ball fromv atleast one contact point at a predetermined yraise'fin, temperature inthe vicinity of the `signal'initiating switch apparatus.

3, A switch cooperative with a magnetic material cornpri'sing a magnetadapted toforrn a closed'magnetic'ir- 20 cuit with s'aidmaterial,metallicfcontacts adjacent "said magnet, and a magnetic ball'fre'elyresting'on and electrically coupling said metallic contacts, saidmagnetic ball being responsive to the opening of the magnetic circuitand the resultant magnetic ux pattern for being displaced from saidmetallic contacts and operating said switch.

4. A switch as claimed in claim 3 for operating when a cover is removedfrom a device, comprising a casing rigidly supporting said magnet, saidcover and casing being integral so that with said cover over saiddevice, said magnet and magnetic material form` a closedma'gneticcircuit, the removal of said cover from said device causing theseparating of said magnet and magneticAk material to open said magneticcircuit'ardactiiate said magnetic ball.

5. A switch as claimed in claim 4 for temperature rei sponse comprisinga bimetallic rstrip Vadjacent said magnetic ball and responsive rtola`temperature change for displacing said ball from said contacts.

